In Memoriam – Tom Gehrels

It is with enormous sadness that I have to pass on the news of the death of Tom Gehrels (1925-2011) during the evening of 11 July.

Professor Gehrels was one of the players in the process that led to the establishment of Spaceguard UK and thence the Spaceguard Centre. As an advisor and mentor Tom was robust, often critical, but always enormously encouraging. His advice was invariably wise, and ignored at peril. The astronomical community has lost a giant character, and a man of great wisdom.

Professor Tom Gehrels joined the UA’s Lunar and Planetary Laboratory (LPL) in 1961 as an Associate Professor. He earned his B.S. in Physics and Astronomy from Leiden (Netherlands) University in 1951, and his Ph.D. in Astronomy and Astrophysics from the University of Chicago in 1956.

While at Chicago, he worked with Subrahmanyan Chandrasekhar and Gerard P. Kuiper (who founded LPL in 1960). Dr. Gehrels’ distinguished science career featured many highlights. During the 1950s, Professor Gehrels pioneered the first photometric system of asteroids and discovered the opposition effect in the brightness of asteroids. In the 1960s, he pioneered wavelength dependence of polarization of stars and planets. His research interests then migrated to imaging photopolarimetry of Jupiter and Saturn, and Dr. Gehrels was named principal investigator for the Pioneer 10 and 11 Imaging Photopolarimeters, which discovered Saturn’s F ring.

In 1980, Tom Gehrels founded the Spacewatch Project, which uses telescopes on Kitt Peak to survey the sky for dangerous asteroids; he led the project until 1997. Professor Gehrels also founded the well known and well respected Space Science Series, still published by the University of Arizona Press. He served as general editor for the first 30 volumes of the series. At its start in the 1980s, the Space Science Series represented a new way of producing research textbooks. In 2007, Tom Gehrels was the recipient of the Harold Masursky Award, presented by the American Astronomical Society’s Division for Planetary Sciences in recognition of meritorious service to planetary science.

Professor Gehrels’ recent research interests were in universal evolution. Each fall, he taught an undergraduate course for non-science majors at the University of Arizona and each spring, he presented a brief version of that course at the Physical Research Laboratory in Ahmedabad, India, where he was a lifetime Fellow.